Materials such as paper, paperboard, plastic, polystyrene, and even metals are presently used in enormous quantity in the manufacture of articles such as containers, separators, dividers, lids, tops, cans, and other packaging materials. Modern processing and packaging technology allows a wide range of liquid and solid goods to be stored, packaged, and shipped in packaging materials while being protected from harmful elements, such as gases, moisture, light, microorganisms, vermin, physical shock, crushing forces, vibration, leaking, or spilling. Many of these materials are characterized as being disposable, but actually have little, if any, functional biodegradability. For many of these products, the time for degradation in the environment can span decades or even centuries.
Each year, over 100 billion aluminum cans, billions of glass bottles, and thousands of tons of paper and plastic are used in storing and dispensing soft drinks, juices, processed foods, grains, beer and other products. In the United States alone, approximately 5.5 million tons of paper are consumed each year in packaging materials, which represents only about 15% of the total annual domestic paper production.
Packaging materials (e.g., paper, paperboard, plastic, polystyrene, glass, or metal) are all, to varying extents, damaging to the environment. For example, the manufacture of polystyrene products involves the use of a variety of hazardous chemicals and starting materials, such as benzene (a known mutagen and a probable carcinogen). Chlorofluorocarbons (or “CFCs”) have also been used in the manufacture of “blown” or “expanded” polystyrene products. CFCs have been linked to the destruction of the ozone layer.
Due to widespread environmental concerns, there has been significant pressure on companies to discontinue the use of polystyrene products in favor of more environmentally safe materials. Some groups have favored the use of products such as paper or other products made from wood pulp. However, there remain drawbacks to the sole use of paper due to the tremendous amount of energy that is required to produce it. A strong need to find new, easily degradable materials that meet necessary performance standards remains.
Degradability is a relative term. Some products which appear to be degraded merely break apart into very small pieces. These pieces are hard to see, but can still take decades or centuries to actually break down. Other products are made from materials which undergo a more rapid breakdown than non-biodegradable products. If the speed of this degradation is such that the product will degrade within a period of less than approximately 24 days under normal environmental conditions, the product is said to be compostable. Achievement of products made of compostable materials which also meet a variety of needs, such as containers for products in a damp or wet condition, has posed a significant challenge.
One solution has been to make packaging materials out of baked, edible sheets, e.g., waffles or pancakes made from a mixture of water, flour and a rising agent. Although edible sheets can be made into trays, cones, and cups which are easily decomposed, they pose a number of limitations. For example, since fats or oils are added to the mixture to permit removal of the sheet from the baking mold, oxidation of these fats cause the edible sheets to go rancid. In general, edible sheets are very brittle and far too fragile to replace most articles made from conventional materials. They are also overly sensitive to moisture and can easily mold or decompose prior to or during their intended use.
Starch is a plentiful, inexpensive and renewable material that is found in a large variety of plant sources, such as grains, tubers, and fruits. In many cases, starch is discarded as an unwanted byproduct of food processing. Starch is readily biodegradable and does not persist in the environment for a significant period after disposal. Starch is also a nutrient, which facilitates its breakdown and elimination from the environment.
Due to the biodegradable nature of starch, there have been many attempts to incorporate it into a variety of materials. Starch has been incorporated into multi-component compositions in various forms, including as filler and binder, as has been used as a constituent within thermoplastic polymer blends.
Starch can be used as a binder or glue to adhere solid constituents together to form a heterogenous mixture of different components. At some point before or during the molding phase, the starch is typically dissolved or gelatinized in an appropriate solvent, such as water, so that the starch becomes a flowable material into which the other components can be dispersed. Since native starch has a melting point that approaches its decomposition temperature, it is necessary to add polar liquids or solvents to allow the starch to become molten, solvated or otherwise liquified into a plastic state at a temperature that is safely below its decomposition temperature. Upon resolidification of the gelatinized starch, typically by removing enough of the water by evaporation so that the starch recrystallizes or otherwise dries out, the starch forms a solid or semi-solid binding matrix that can bind the remaining components together. Although many have attempted for years to perfect a starch blend that would yield an environmentally sound material while, at the same time, being economical to make, such a combination has not yet been achieved.
There remains a need in the art to provide a fully compostable product that is strong, not prone to mold or pests, and can be readily and inexpensively made. Furthermore, there is a need to develop a robust method to develop compostable products that can be used to hold dry, wet or damp material at a range of temperatures.
PCT Publication No. WO 99/02598, filed by Business Promotions, Inc., describes a method for making a biodegradable product for use as a container for foodstuffs, including hot and cold liquids. The product is manufactured under pressure and heat in a mold, based on a basic material made of amylose-comprising flour derived from an edible crop plant, wood flour, natural wax and water. The basic material consists substantially of a moist granulate comprising 50–250 parts by weight flour, 10–85 parts by weight wood flour, 2–30 parts by weight natural wax and 50–250 parts by weight water.
European Patent 0773721B1 to Coöperatieve Verkoop discloses compounds made of a starch suspension and a wax coating, which is baked into a base mold. The coating is made of a wax composition comprising at least 50% wax and having a melting temperature of at least 40° C. The starch composition is preferably made by a process that includes 5–75% of a starch derivative which has a reduced swelling capacity at increased temperatures when compared to native starch.
PCT Publication No. WO 01/60898, filed by Novamont describes products such as sheets of different thicknesses and profile based on destructured or complexed starch, which are biodegradable. In particular, the patent claims partly-finished products, for example a foam sheet material, comprising destructured or complexed starch foamed as a continuous phase, having a density between 20 and 150 kg/m3, cell dimensions in a range between 25 and 700 μm with a cell distribution such that 80% of them have a dimension between 20 and 400 μm.
U.S. Pat. No. 6,451,170 to Cargill, Inc. describes improved starch compositions of cross-linked cationic starch, used in the papermaking process. The '170 patent claims the following papermaking process: 1) providing a cationized cross-linked starch component having a hot paste viscosity in the range of from about 200 cps to about 3000 cps as measured in a Brookfield viscometer at about 95° C. using a No. 21 spindle; 2) cooking a first portion of the starch component to generate a cooked starch component at an average cooking temperature below 330° F. for a period of time; 3) dewatering a paper furnish (the paper furnish including: (i) cellulosic fibers in an aqueous slurry, (ii) inorganic particles comprising at least 50 percent by weight particles having an average particle size of no greater than 1 micron, and (iii) the cooked starch component); and 4) adjusting the dewatering rate by cooking a second portion of the starch component at an average temperature at least 10° F. different than the first cooking temperature. The fourth step in the papermaking process can also include adjusting the first pass retention during dewatering by cooking a second portion of the starch composition at an average temperature at least 10° F. different than the first cooking temperature.
U.S. Pat. No. 5,122,231 to Cargill, Inc. describes a new cationic cross-linked starch for use in papermaking in the wet end system of a paper machine using a neutral or alkaline finish. The '231 patent claims methods to increase starch loading capacity in a papermaking process in which the papermaking process has a pH of about 6 or greater. One method is directed to adding the cationized cross-linked starch to a paper furnish of the process prior to the conversion of the furnish to a dry web wherein the starch is cationized to a degree of substitution on the hydroxyl groups of the starch between about 0.005 and about 0.050 and wherein after the cationization the starch is cross-linked to a hot paste viscosity in the range of from about 500 cps to about 3000 cps as measured on a Brookfield viscometer at about 95° C. using a No. 21 spindle. Another method is directed to adding cationized cross-linked starch to a paper furnish of the process in an amount effective for making Zeta potential of the furnish about zero and wherein the starch is cationized with monovalent cations and has a degree of substitution of monovalent cations on the hydroxyl groups of the starch between about 0.005 and about 0.050 and wherein after cationization the starch is cross-linked to a hot paste viscosity in the range of from about 500 cps to about 3000 cps as measured on a Brookfield viscometer at about 95° C. using a No. 21 spindle.
U.S. Pat. Nos. 5,569,692 and 5,462,982, both assigned to Novamont, disclose a composition for a biodegradable material which can be used at high temperatures comprising destructured starch, a thermoplastic polymer, and a plasticizer having a boiling point higher than 150° C. in an amount from 20 to 100% based on the weight of starch, said destructured-starch being obtained by destructuring starch as it is, without the addition of water. The inventors found that if a starch is destructured as it is, with the addition of a high-boiling plasticizer (such as glycerine) and a destructuring agent (such as urea), in an extruder heated to a temperature below the boiling point of the plasticizer (but between 120 and 170° C.), destructured starch compositions are obtained which can be mixed with polymers having relatively high melting points and are suitable for extrusion at temperatures higher than 120° C. at low pressure. The compositions thus obtained are particularly suitable for subsequent operations such as thermoforming and blowing.
U.S. Pat. No. 5,252,271 to Bio-Products International discloses a material that is based on a dry starch composition, having no greater than 30% water content; which is mixed with a mild acid in dry, powdered form (preferably malic acid, tartaric acid, citric acid, maleic acid and succinic acid) at a percentage of 0.2 to 7% of the total starch composition. Adding a dry, powdered carbonate composition capable of reacting with acid to generate CO2 gas at a composition percentage of 0.1 to 2% of the total starch composition and mixing and advancing the product with water within an extrusion barrel of the extrusion means to generate elevated heat and pressure for converting the material to a gelatinous state that can be dried and remain pliable.
U.S. Pat. No. 4,863,655 to National Starch and Chemical Corp. discloses a biodegradable packaging material comprising an expanded, high amylose starch product having at least 45% (by weight of the final material) amylose content and a low density, closed cell structure with good resilience and compressibility. Another embodiment provides a method of preparing the packaging material with a total moisture content of 21% or less by weight, at a temperature of from 150 to 250° C.
U.S. Pat. No. 5,428,150 to Cerestar Holdings discloses a method for making a starch-containing composition to produce a material suitable for the production of molded articles in which the composition contains in addition to the starch a starch degradation product selected from starch hydrolysis products having dextrose equivalent's of 1 to 40, particularly a maltodextrin, oxidized starches and pyrodext.
U.S. Pat. Nos. 5,660,900, 5,868,824, and PCT Publication No. WO 96/05254 filed by Khashoggi disclose compositions for manufacturing biodegradable articles from highly inorganically filled materials having a starch-based binder. These documents describe articles of manufacture that have high levels of the inorganic filler in a polymer matrix without adverse affects on the properties of the binding system. The articles contain a matrix of starch and at least one inorganic aggregate, present as at least about 20% by weight (or 5% by volume) of the final mixture. The matrix is prepared from about 10 to 80% of a starch-based binder that has been substantially gelatinized by water and then hardened through the removal of a substantial quantity of the water by evaporation with an inorganic aggregate dispersed throughout the starch-bound cellular matrix. The mixture is designed with the primary considerations of maximizing the inorganic components, minimizing the starch component and solvent, and selectively modifying the viscosity to produce articles that have the desired properties for their intended use.
U.S. Pat. Nos. 5,736,209 and 5,810,961, and PCT Publication No. WO 97/37842, also assigned to Kashoggi Industries, disclose methods to develop biodegradable paper and products which include a binding matrix of starch and cellulosic ether, and fibers substantially homogeneously dispersed throughout the matrix. The '209 patent discloses a concentration range for the starch of about 5% to about 90% by weight of solids in the sheet, for the cellulosic ether a range from about 0.5% to about 10% by weight of solids, and for fibers a concentration range from about 3% to about 40%. Optionally, an inorganic mineral filler can be added. Sheets produced using this biodegradable material having a thickness less than about 1 cm and a density greater than about 0.5 g/cm3 are described.
PCT Publication No. WO 01/51557, also filed by Khashoggi, is directed to compositions and methods for manufacturing thermoplastic starch compositions having a particulate filler (present in an amount greater than about 15% by weight of the thermoplastic starch) and, optionally, fiber reinforcement. Native starch granules are made thermoplastic by mixing and heating in the presence of an appropriate plasticizer (including somewhat polar solvents such as water or glycerin) to form a starch melt. The starch melt is then blended with one or more non-starch materials in order to improve the properties and reduce the cost of the resulting thermoplastic starch composition. A particulate filler component is thereafter blended with the starch melt, preferably an inexpensive, naturally occurring mineral particulate filler (“inorganic filler”), included in an amount greater than about 15% by weight of the thermoplastic starch composition. In addition, this reference discloses a composition comprising a thermoplastic starch melt having a water content of less than about 5% by weight while in a melted state, wherein at least one plasticizer has a vapor pressure of less than about 1 bar when in a melted state and in which a solid particulate filler phase is dispersed and included in an amount from about 5% to about 95% by weight. An additional embodiment discloses dispersion of a solid particulate filler phase in an amount from about 5% to about 95% by weight of the thermoplastic starch composition and a fibrous phase in a concentration of from about 3% to about 70% by weight.
U.S. Pat. No. 6,168,857 to Khashoggi Industries discloses a starch-bound sheet having a thickness less than about 1 cm and a density greater than about 0.5 g/cm3 comprising: (a) a binding matrix including starch and an auxiliary water-dispersible organic polymer, wherein the starch has a concentration greater than about 5% by weight of total solids in the sheet; and (b) fibers substantially homogeneously dispersed throughout the starch-bound sheet; and optionally an inorganic mineral filler.
U.S. Pat. Nos. 5,618,341, 5,683,772, 5,709,827, and 5,679,145 and PCT publication No. WO 97/2333, assigned to Khashoggi Industries, disclose starch-based compositions that can be used in making containers. U.S. '341 and '145 teach methods for dispersing fibers within a fibrous composition comprising the steps of: (a) combining together water, fibers, and a thickening agent such that the thickening agent (such as a pregelatinized starch) and water interact together to form a fluid fraction that is characterized by a yield stress and viscosity that enables the fibers to be substantially uniformly dispersed throughout the fibrous composition as the fibers and fluid fraction are mixed together, the fibers having an average length greater than about 2 mm and an average aspect ratio greater than about 25:1; and (b) mixing together the combined thickening agent, water, and fibers in order to substantially uniformly disperse the fibers throughout the fibrous composition. The thickening agent is included in an amount in a range from about 5% to about 40% by weight of the fluid fraction. The inventive method involves a fluid system that is able to impart shear from a mechanical mixing apparatus down to the fiber level in order to obtain a starch-based composition having substantially uniformly dispersed fibers. U.S. patent '772 additionally discloses an inorganic filler to enhance the strength and flexibility of the articles. '827 additionally discloses methods to make the article of manufacture that is developed from mixtures including fibers having an average aspect ratio greater than about 25:1. The '341, '772, '827, and '145 patents and WO 97/2333 application disclose high aspect ratios (i.e., about 25:1 or greater) and long-length (i.e., at least about 2 mm) fibers to reinforce the structure. PCT publication No. WO 97/23333 discloses articles that contain high starch contents (from about 50% to about 88% by weight ungelatinized and about 12% to about 50% by weight of gelatinized starch).
U.S. Pat. No. 6,303,000 to Omnova Solutions discloses a method to improve the strength of paper by adding an aqueous cationic starch dispersion modified with a blocked glyoxal resin to a paper pulp slurry. The starch dispersion is prepared by gelatinizing an aqueous suspension of starch granules (including potato, corn, waxy corn, red and white milo, wheat and tapioca, thin-boiling starches, and starches that have been additionally chemically modified) and reacting the starch with a blocked glyoxal resin at temperatures of at least 70° C., preferably 85 to 95° C. Suitable blocked glyoxal resins which can be used with the invention include cyclic urea/glyoxal/polyol condensates, polyol/glyoxal condensates, urea or cyclic urea/glyoxal condensates and glycol/glyoxal condensates in an amount from about 3% to about 30%, preferably 9 to 20%, of the total dry weight of starch. The resulting gelatinized starch composition can be cooled and stored, or directly added to a dilute paper pulp slurry to increase the tensile strength and elasticity of the resulting paper product.
PCT Publication No. WO 01/05892 filed by Kim & Kim describes methods for manufacturing plastic-substitute goods by using natural materials by preparing a glue made by mixing 20% by weight of a starch and 80% by weight of water together, heating this mixture; washing and drying rice husks to a drying extent of 98%; mixing the glue and the rice husks together so as to form a mixture of the glue and the rice husks, drying them to a drying extent of 98%, and crushing them to a size range of 0.01–0.1 mm. Then, mixing 80% by final weight of the mixture of the glue and the rice husks, 5% by final weight water, and 15% by final weight of rosin to form a final mixture; and molding the final mixture using a molding machine at a temperature of 100–350° C. under a pressure of 5 kg/cm at a production frequency of 30–80 seconds per product.
PCT Publication No. WO 02/083386 also filed by Kim & Kim describes methods for manufacturing plastic-substitute goods by using natural materials using a starch-based glue and melamine resin. Melamine or urea resin is a thermosetting resin which is formed by reaction of melamine or urea acting upon formaldehyde. The products are manufactured by first preparing a mixture of 20% by weight of a starch and 80% by weight of water, heating this mixture; washing and drying rice husks to a drying extent of 98%; mixing the glue and the rice husks together so as to form a mixture of the glue and the rice husks, drying them to a drying extent of 98%, and crushing them to a size range of 0.01–0.1 mm. Melamine resin is obtained by a process of first, mixing 30% by weight of formaldehyde solution and 70% by weight of water, 30% by weight of melamine or urea and heating the mixture at a temperature of 350° C. A mixture is then made of 70% by final weight of the mixture of the glue and the rice husks, 15% by weight of water, and 15% by weight of melamine resin to form a final mixture. The final mixture is molded by a molding machine at a temperature of 100 350° C. under a pressure of 5 kg/cm at a product ion frequency of 30–80 seconds per product.
U.S. Publication No. U.S. 2002/0108532 and PCT Publication No. WO 00/39213 filed by Apack AG disclose methods to produce a shaped body made of biodegradable material that shows good expansion behavior during thermoforming from 7.6 to 8.5% by weight of cellulosic fibers, from 16.1 to 17.6% by weight of native starch, from 5.4 to 6% by weight of pregelatinized starch and from 68.0 to 70.6% by weight of water. First, the pregelatinized starch is produced by mixing between 5.4–6% starch and 94–94.6% water, heating the mixture to 68–70° C., holding the mixture constant at 68–70° C. for 10 minutes, and cooling the pregelatinized starch to 50° C. Then, adding the 16.1 to 17.6% by weight of native starch, 7.6 to 8.5% by weight of cellulosic fibers, and 68.0 to 70.6% by weight of water to the pregelatinized solution at a temperature of 50° C.; mixing for 5 minutes to achieve a homogeneous mixture at 40° C., not allowing the mixture to substantially cool, and placing the mixture in a baking mold, and baking the mixture at 100–200° C. for 10–100 seconds to form the shaped body.
German patent DE 19,706,642 to Apack Verpackungen Gmbh discloses the production of a biodegradable article from 25–75% fibers, 13–38% starch and 13–38% water. First, the 25–75% fibers, 13–38% starch are mixed in a dry state in a continuous process; then water is admixed continuously. The mixture is then subjected to a baking process to obtain the finished molded article, and then the molded article is coated with a biologically degradable film that is impermeable to humidity.
Although numerous attempts have been made to provide suitable biodegradable and compostable materials for packaging, the resulting substances are not ideal. The currently available materials either cannot successfully be used to package materials, particularly those that are wet, or do not effectively degrade under normal environmental conditions. A need exists to develop materials that will reduce the build up of disposed, slowly degrading materials, and to limit the environmental damage caused by toxic chemicals used in the production of packaging materials.
It is therefore an object of the present invention to provide a robust process and materials for the production of an efficiently biodegradable container.
It is a further object of the present invention to provide a materials and a process for producing a biodegradable container that can hold products in dry, wet or damp conditions.
It is another object of the present invention to provide material and a process to produce biodegradable containers through the use of a pregelatinized starch solution that is stable at a wide range of temperatures.
It is a further object of the present invention to provide a process and material to produce biodegradable containers through the use of a pregelatinized paper starch solution that is stable at a wide range of temperatures.
It is another object of the present invention to provide a process and material to produce biodegradable containers from a wide range of materials.
It is yet another object of the present invention to provide a process and material to produce biodegradable containers under a wide range of environmental conditions.
It is still another object of the present invention to provide biodegradable and compostable products.